US11619541B2 - Vehicle speed, direction, and size measurement using temporal distributed fiber optic sensing - Google Patents
Vehicle speed, direction, and size measurement using temporal distributed fiber optic sensing Download PDFInfo
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- US11619541B2 US11619541B2 US17/227,325 US202117227325A US11619541B2 US 11619541 B2 US11619541 B2 US 11619541B2 US 202117227325 A US202117227325 A US 202117227325A US 11619541 B2 US11619541 B2 US 11619541B2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
-
- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/0104—Measuring and analyzing of parameters relative to traffic conditions
- G08G1/0108—Measuring and analyzing of parameters relative to traffic conditions based on the source of data
- G08G1/0116—Measuring and analyzing of parameters relative to traffic conditions based on the source of data from roadside infrastructure, e.g. beacons
-
- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/015—Detecting movement of traffic to be counted or controlled with provision for distinguishing between two or more types of vehicles, e.g. between motor-cars and cycles
-
- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/017—Detecting movement of traffic to be counted or controlled identifying vehicles
-
- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/02—Detecting movement of traffic to be counted or controlled using treadles built into the road
-
- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/052—Detecting movement of traffic to be counted or controlled with provision for determining speed or overspeed
-
- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/056—Detecting movement of traffic to be counted or controlled with provision for distinguishing direction of travel
Definitions
- This disclosure relates generally to distributed fiber optic sensing (DFOS) systems, methods, and structures that provide real-time vehicle speed, direction, and size measurement.
- DFOS distributed fiber optic sensing
- DFOS distributed fiber optic sensing systems
- systems, methods, and structures according to aspects of the present disclosure employ a novel and nonobvious layout of the sensing fiber that permits the association of a vehicle's geometric properties to its temporal behavior.
- FIG. 1 is a schematic diagram of an illustrative distributed fiber optic sensing system and operation generally known in the art
- FIG. 2 is a schematic flow diagram illustrating an operational execution of a method according to aspects of the present disclosure
- FIG. 3 is a schematic diagram of an illustrative layout of optical fiber beneath highway and/or roadway pavement according to aspects of the present disclosure
- FIG. 4 is a schematic diagram of the illustrative layout of optical fiber beneath highway and/or roadway pavement of FIG. 3 and example vehicle tracks according to aspects of the present disclosure
- FIG. 5 is a schematic diagram of an illustrative layout of optical fiber beneath highway and/or roadway pavement in “series” for multi-lane highway/roadway application according to aspects of the present disclosure
- FIG. 6 is a schematic block diagram of an illustrative layout of optical fiber illustrating certain critical sensing parts/segments of the layout according to aspects of the present disclosure.
- FIG. 7 is a schematic block diagram of an illustrative modified layout of optical fiber adapted for longer pulse DAS system according to aspects of the present disclosure.
- FIG. 8 is a block diagram of illustrative features provided by systems, methods, and structures according to aspects of the present disclosure.
- FIGS. comprising the drawing are not drawn to scale.
- FIG. 1 is a schematic diagram of an illustrative distributed fiber optic sensing system generally known in the art—we begin by noting that distributed fiber optic sensing (DFOS) is an important and widely used technology to detect environmental conditions (such as temperature, vibration, stretch level etc.) anywhere along an optical fiber cable that in turn is connected to an interrogator.
- DFOS distributed fiber optic sensing
- contemporary interrogators are systems that generate an input signal to the fiber and detects/analyzes the reflected/scattered and subsequently received signal(s). The signals are analyzed, and an output is generated which is indicative of the environmental conditions encountered along the length of the fiber.
- the signal(s) so received may result from reflections in the fiber, such as Raman backscattering, Rayleigh backscattering, and Brillion backscattering. It can also be a signal of forward direction that uses the speed difference of multiple modes. Without losing generality, the following description assumes reflected signal though the same approaches can be applied to forwarded signal as well.
- a contemporary DFOS system includes an interrogator that periodically generates optical pulses (or any coded signal) and injects them into an optical fiber.
- the injected optical pulse signal is conveyed along the optical fiber.
- a small portion of signal is reflected and conveyed back to the interrogator.
- the reflected signal carries information the interrogator uses to detect, such as a power level change that indicates—for example—a mechanical vibration.
- the reflected signal is converted to electrical domain and processed inside the interrogator. Based on the pulse injection time and the time signal is detected, the interrogator determines at which location along the fiber the signal is coming from, thus able to sense the activity of each location along the fiber.
- a DAS Distributed Acoustic Sensor
- the vibration at the point of interest will be sampled at 20 kHz frequency which—as those skilled in the art will understand and appreciate—is able to cover frequency of up to 10 kHz according to Nyquist rule.
- the temporal width of the optical pulse used in a DAS/DVS system is usually one of the critical parameters to determine the spatial resolution of the DAS/DVS system. In order to achieve high spatial resolution, one employs a shorter optical pulse.
- systems, methods, and structures according to aspects of the present disclosure overcome this and other deficiencies in the art by achieving a high spatial resolution measurement without requiring a short pulse and instead by using a temporal measurement.
- systems, methods, and structures according to aspects of the present disclosure achieve extreme high accuracy spatial measurement via a temporal measurement—which advantageously and surprisingly relieves any burden on the constraints of the DAS or the DVS system.
- FIG. 2 is a schematic flow diagram illustrating an operational execution of a method according to aspects of the present disclosure.
- a method according to aspects of the present disclosure is initiated when a vehicle axle passes over an inventive layout of an DFOS optical fiber—located under a roadway.
- Our method determines the properties of the axle namely, its speed, its direction, and its width. If the width is less than a predetermined threshold value, then the vehicle of which the axel is a component is determined by the system to be a motorcycle. The system then waits for the next vehicle axle to pass over the DFOS optical fiber. The same parameters are determined for this next axle along with a distance between this next (second) axle and the previous (first) axle.
- this second, next axle is determined to be a new (different) vehicle. If the two parameters of the two axles are not sufficiently large, they are determined to be part of a same vehicle and the axle number is counted. This procedure is shown schematically in the flow chart in the figure.
- FIG. 3 is a schematic diagram of an illustrative layout of optical fiber beneath highway and/or roadway pavement according to aspects of the present disclosure.
- the illustrative layout may be described generally as a “diamond in a box” layout formed by the optical fiber layout, wherein no part of the optical fiber layout overlies itself.
- one illustrative layout may be thought of as two concentric squares—one inside another—each having an opening—the inner one (with shorter side lengths) rotated 45 degrees, all defining a continuous, non-overlapped, optical fiber path constructed from optical fiber cable positioned under a roadway/highway.
- the illustrative layout may be considered as comprising eight sections.
- FIG. 4 is a schematic diagram of the illustrative layout of optical fiber beneath highway and/or roadway pavement of FIG. 3 and example vehicle tracks according to aspects of the present disclosure.
- a two axle vehicle is traversing over an illustrative optical fiber layout that is a sensor fiber for a DFOS.
- the vehicle wheel track is illustrated by the two parallel lines.
- the unknowns include: the speed of the vehicle, the angle ⁇ (vehicle direction), the distance of the vehicle wheel track to the center of lane ( ⁇ ) (to calculate the axle width), and the number of axles.
- the known parameters include: the spacing ⁇ and all the angles in the fiber layout.
- Assumptions include: the vehicle travels with constant velocity when passing over the fiber layout, the vehicle stays inside its lane, the angle ⁇ (driving direction) is between 45-135 degrees, and the vehicle does not move forward and backward.
- each wheel (tire) overruns/passes over/through the fiber layout and creates a linear track in three sections (s1, s2, and s3) as shown in the figure.
- the DFOS/Distributed Acoustic Sensing (DAS) system does NOT record or detect the point of contact of a tire on the fiber layout. Instead, the DAS system ONLY records the TIME of contact of the tire to different parts of the fiber layout. Those are shown in the figure as t1, t2, t3, and t4.
- the driving direction can be calculated according to the following:
- tan ⁇ ( ⁇ - 4 ⁇ 5 ) t ⁇ 4 - 2 ⁇ t ⁇ 2 2 ⁇ t ⁇ 3 - t ⁇ 4
- axle width ⁇ right + ⁇ left
- tan ⁇ ( ⁇ ) s ⁇ 2 + s ⁇ 3 - s ⁇ 1 s ⁇ 2 + s ⁇ 1 - s ⁇ 3 which can be simplified to
- tan ⁇ ( ⁇ ) t ⁇ 4 - 2 ⁇ t ⁇ 2 2 ⁇ t ⁇ 3 - t ⁇ 4 which is the formula defining the driving direction.
- this ⁇ parameter may be used to determine the axle width of the vehicle. Note that all of the above determinations/calculations will be done for both left and right sides of a track.
- FIG. 5 is a schematic diagram of an illustrative layout of optical fiber beneath highway and/or roadway pavement in “series” for multi-lane highway/roadway application according to aspects of the present disclosure. As shown in that figure, the illustrative layout described previously is extended in substantially a “series” arrangement, such that “three diamond” layouts are made in a three lane highway, the layout having a single input and single output and—like before—none of the fiber overlies itself.
- FIG. 6 is a schematic block diagram of an illustrative layout of optical fiber illustrating certain critical sensing parts/segments of the layout according to aspects of the present disclosure. As shown in the figure, segments 1 - 6 and 8 are particularly critical to our inventive sensing layout as noted previously.
- FIG. 7 is a schematic block diagram of an illustrative modified layout of optical fiber adapted for longer pulse DAS system according to aspects of the present disclosure. As shown in this figure, at several transition/extension points from one of the sections identified previously to a next section, the fiber is arranged in one or more loops of fiber. As such, the loops will overlie a portion of the fiber itself.
- FIG. 8 is a block diagram of illustrative features provided by systems, methods, and structures according to aspects of the present disclosure. As may be observed from this figure, our inventive systems, methods, and structures according to aspects of the present disclosure provide for sophisticated traffic measurement and monitoring by DFOS using our optical fiber layout(s) described. Our illustrative disclosure provides for the time domain measurement and further determination vehicle type(s) and properties from temporal data.
- systems, methods, and structures according to aspects of the present disclosure advantageously permit: detection/determination of vehicle speed, detection/determination of vehicle direction, detection/determination of axle width, detection/determination of motorcycles, detection/determination of a number of axles on a given vehicle, detection/determination of these in a multi-lane highway, and an ability to modify the fiber layout for enhanced/longer pulse widths.
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Abstract
Description
α=t2v cos(γ)√{square root over (2)},
where γ=θ−45.
axlewidth=αright+αleft
s1 cos(γ)+s1 sin(γ)+s2 sin(γ)=β√{square root over (2)}
s2 cos(γ)+s3 sin(γ)+s3 cos(γ)=β√{square root over (2)}
s1=(t2−t1)v; s2=(t3−t2)v
s3=(t4−t3)v; t1=0; γ=θ−45
(s2+s1−s3)sin(γ)=(s2+s3−s1)cos(γ)
which can be simplified to
which is the formula defining the driving direction.
which in turn allows the average speed of the vehicle to be determined by:
α=s1 cos(γ)√{square root over (2)}
which can be simplified as:
α=t2 v cos(γ)√{square root over (2)}
Claims (10)
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US17/227,325 US11619541B2 (en) | 2020-04-14 | 2021-04-11 | Vehicle speed, direction, and size measurement using temporal distributed fiber optic sensing |
PCT/US2021/026770 WO2021211396A1 (en) | 2020-04-14 | 2021-04-12 | Vehicle speed, direction, and size measurement using temporal distributed fiber optic sensing |
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US202063009679P | 2020-04-14 | 2020-04-14 | |
US17/227,325 US11619541B2 (en) | 2020-04-14 | 2021-04-11 | Vehicle speed, direction, and size measurement using temporal distributed fiber optic sensing |
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GB202117090D0 (en) * | 2021-11-26 | 2022-01-12 | Fotech Group Ltd | Monitoring traffic |
CN115410403B (en) * | 2022-04-19 | 2023-11-10 | 北京见合八方科技发展有限公司 | Road vehicle positioning tracking method and device based on passive perception and readable medium |
Citations (7)
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KR20000023722A (en) * | 1996-07-12 | 2000-04-25 | 스프레이그 로버트 월터 | Fiber optic current sensor with bend birefringence compensation |
US20040080432A1 (en) * | 2001-02-15 | 2004-04-29 | Hill David J | Road traffic monitoring system |
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US20170358205A1 (en) * | 2016-06-09 | 2017-12-14 | William Ippolito | Smart Loop Treadle |
KR20190054788A (en) * | 2017-11-14 | 2019-05-22 | 한국광기술원 | axle number and weight detecting apparatus using optical fiber sensor cable |
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GB201519202D0 (en) * | 2015-10-30 | 2015-12-16 | Optasense Holdings Ltd | Monitoring traffic flow |
KR102087688B1 (en) * | 2018-11-13 | 2020-03-11 | 한국광기술원 | optical fiber sensor measuring weight of car and contact position |
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- 2021-04-12 WO PCT/US2021/026770 patent/WO2021211396A1/en active Application Filing
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KR20000023722A (en) * | 1996-07-12 | 2000-04-25 | 스프레이그 로버트 월터 | Fiber optic current sensor with bend birefringence compensation |
US20040080432A1 (en) * | 2001-02-15 | 2004-04-29 | Hill David J | Road traffic monitoring system |
US20060257066A1 (en) * | 2003-09-24 | 2006-11-16 | Qinetiq Limited | Fibre-optic surveillance system |
US20140249711A1 (en) * | 2013-03-04 | 2014-09-04 | International Road Dynamics | System and method for measuring moving vehicle information using electrical time domain reflectometry |
US20170358205A1 (en) * | 2016-06-09 | 2017-12-14 | William Ippolito | Smart Loop Treadle |
US20190206240A1 (en) * | 2017-08-16 | 2019-07-04 | Velsis Sistemas E Tecnologia Viaria S/A | System for monitoring dynamic weighing and speed of vehicles on lanes |
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